Multi-Purpose, Extra Long Battery Life Boom Box

Built: 2009/10/XX
Added to Webpage: 2010/08/02

I had a pair of computer speakers that had come with an IBM Aptiva computer that I used back in 1996.
The speakers connected to a +12V lead from the computer's power supply.
The computer eventually went obsolete, so I salvaged the speakers for camping.
At first, I used a bunch of soldered-together cells from a couple laptop batteries to power the speakers.
When I was a member of the UVic Autonomous Underwater Vehicle Team, I built some waterproof tubes that held 6 D cells for the AUV, so, one day, I used a pair of them to power the speakers, and I managed to track down a picture of the setup.

2005_07_22: The IBM Aptiva speakers hooked up to the AUV's battery tubes:

Later, my dad gave me a pair of used wheelchair batteries after he installed new batteries in someone's wheelchair.
One battery was dead, but the other one was good.
For a while, I carried the battery and speakers separately out camping, then wired them up at the site, and then disassembled them to pack them up to go home.
I decided to permanently wire them together.
Sometime in 2007, I put the wheelchair battery, the speakers, an inverter, and a power bar on a sheet of plywood and strapped them together with hot glue and string.
I managed to track down a few pictures:

2007/08/24:

Here is a picture of the stereo powering a laptop:

I later added a pouch to hold my Rio Volt SP250 MP3 CD player and USB ports to power iPods and my Sandisk Sansa MP3 player:

Some cool features of the stereo:
It could not only be recharged by car battery chargers, but it could be connected to a car’s battery through jumper cables and charged at the campground by idling the engine. It could be used to jump-start a car with a dead battery (and was used several times for such). It could be used to recharge cell phones through the USB ports, the 12V cigarette lighter socket, or the 120V ac wall plugs. It could run a trouble light with a compact fluorescent light in it for a long time (useful for setting up camp in the dark). It could power laptop computers.

A lot of people loved my stereo and wanted me to build one for them.
I had trouble tracking down affordable, loud, 2-channel computer speakers, like the old IBM ones I was using, so I decided on building a custom speaker box and use car audio equipment.
I had a pair of Pyramid 6908GS 6X9 speakers that I had salvaged from my old car before getting it towed to the auto wreckers.
I originally got them from a London Drugs Boxing Day sale, but London Drugs didn't sell speakers anymore.
I wanted to make multiple stereos, so I had to make sure that all of the parts that I used in this design were available for purchase.
I managed to find a company in Canada that sold them for a decent price: http://fcsurplus.ca/shopping/shopexd.asp?id=99
I wanted to be able to play MP3 CDs and also have an amplifier that could take an input signal from an earphone jack, so that I could use my MP3 player.
After searching around, I decided that the cheapest and simplest solution was just to use a car CD deck.
As a bonus, they also come with a built-in radio.
I bought one for $100, which seemed to be the cheapest price available at several stores in Victoria, but I regret not spending a little bit more and get one that also had an iPod connector.
Recently, I found a secret cheaper source, but only in limited quantities at certain times of the year.
I bought a 2-port, 12V cigarette lighter socket at Canadian Tire.
I reused my old 300-Watt inverter from Canadian Tire, but I think new ones go on sale for $35 sometimes.
I reused the USB ports from my old stereo, but forgot to look for a source for new ones.
I reused the battery, but found a source for new ones.
I forgot the name of the store, but remembered that it was located beside the Callwood Subway:

Capacity

Length

Depth

Height without Posts

Height with Posts

Weight

Price

Battery 1

33 AH

7 3/4"

5 1/8"

6 5/16"

7 1/8"

26lb, 10oz

$109.99

Battery 2

45 AH

7 3/4"

6 9/10"

6 11/16"

6 11/16"

32lb, 6oz

$146.99

Difference

1.36X

0

1 7/16"

3/8"

-7/16"

1.22X

1.34X

The one that I had was a 33 amp hour battery, similar to the one in the table above.
That size of battery was also often advertised as 35 amp hour, so I managed to find a cheaper source as a 35 AH battery, but it was in the US, and the shipping costs were huge:
Ebay

I constructed the new stereo, shown in the image below:

I tried to design it to handle a small amount of rain, but also give the CD deck air ventilation for cooling.
I bought some 1/2" thick, sanded plywood and painted it with a weatherproof sundeck coating before constructing the stereo out of it.
The CD deck was covered from rain from above, but open at the front and back, and with a gap above and below it for airflow.
The deck was suspended above the floor below it to avoid being in contact with any water that could possibly pool there.
The battery and inverter chamber above had drain holes drilled to drain to the outside of the stereo.
The inverter was exposed to weather though.
I planned to add some kind of fold-over plastic cover, but haven't implemented it yet.
The handle consisted of 1" doweling, wrapped in hockey tape.
The doweling was screwed, and glued to two 3/4" X 1/2" X 3" pieces of wood.
These pieces of wood were screwed into the top of the stereo.
The whole stereo was glued together using outdoor glue.
The only screws used were the screws of the removable handle, which had to be removed in the case of battery replacement, and the speaker screws.
Before inserting the speakers, the speaker boxes were ceiled on the inside using silicon glue.
The speaker wire holes were also sealed using silicon glue.
The area where the speakers contacted the case was also pre-siliconed before screwing the speakers to the case.

Here is a picture of the back of the stereo:

Below is a close-up of the car CD deck, showing how it is suspended above the plywood below it.

Below is a picture, showing the top of the stereo. The handle, wheelchair battery, inverter, 12V lighter sockets, USB ports, and radio antenna are visible.

Below is a picture, showing the top of the stereo, from the rear point of view.

Click the image below to view a .PDF file containing the plans to make the wood part of the stereo:

I was impressed by loudness of the stereo, and the improved base over the old one, but I was disappointed by the size and weight.
It didn't fit into the same cubbyhole in my car as the old one, and it was awkward to carry through a furniture-filled room, doorway, or skinny hallway.
The parts costs were so expensive, and the wood working, wiring, and multi-step gluing was so time consuming, that the current design wasn't viable for profitable mass-production of the stereo.
The old stereo’s whisper-volume current consumption was 180 ma, and the new stereo’s whisper-volume current consumption was 250 ma, which equates to 7.6, and 5.5 days running time respectively.
I defined each system's efficient loud volume as double the whisper volume, which equates to 360ma and 500ma respectively, which equates to 3.8 and 2.7 days respectively.
The stereo went much louder than the efficient loud volume, but I was unable to measure the power consumption at the peak volume because the multimeter added series resistance to the power path and caused audio distortion that didn't exist when run without the multimeter.
In most situations, a higher volume than the efficient loud volume was unnecessary.
The CD deck was advertised as a 4-channel * 50 watt-per-channel deck, of which, I was only using 2 channels.
If I was aiming to maximize the volume out of the deck, I would have used four 6 1/2" speakers instead of two 6" X 9" speakers.
Although four 6 1/2" speakers would theoretically only increase the speaker surface area by a factor of 1.33 over two 6" X 9" speakers, I think it could double the peak power by utilizing the other 2 channels.
The four 6.5" speaker design would add 1.5" to the overall height of the design.
Several friends were impressed by the sound coming out of the stereo, and they couldn't believe that it was coming out of Pyramid speakers, which was a low end brand.
I found some cheep speakers with better specs than the Pyramid ones advertised here: http://fcsurplus.ca/shopping/shopexd.asp?id=8194, but
I don't trust the marketing department of cheep component manufactures, so I'm debating whether to try them out or stick with the decent Pyramid speakers.
If going the 6.5" speaker rout, I found these: http://www.fcsurplus.ca/shopping/shopexd.asp?id=47, and these: http://fcsurplus.ca/shopping/shopexd.asp?id=15485
I have thought of making a jig to speed up the gluing steps, and simplifying the design to make the stereo smaller, so I think I might be able to finally make production profitable.